PHOENIX—The two most important words associated with the Team USA in this World Baseball Classic are ones few believed would be needed.

Run differential.

Those words are what Joe Torre and his band of big leaguers have to be concerned with after Mexico dumped the United States, 5-2, Friday night at Chase Field in the first round of the WBC. With this loss, the Americans might not control their own fate even if they win their next two games.

What could be more surprising is that if Mexico, which has played well in its two games outside of a bad ninth inning Thursday, can beat Canada on Saturday afternoon, then Team USA takes the field for its second game facing elimination against Italy, the surprise of Pool D with two wins already in its back pocket.

That could be disastrous for the United States, a team supposedly “built to win” by Torre after two disappointing tournaments before this one.

“We have to win tomorrow,” Torre said. “This is the postseason approach.”

This was a game the United States was expected to win, just as they are expected to win Saturday and Sunday. But unfulfilled expectations have been the story of Team USA’s WBC life.

“We grieve this for the rest of the night,” said USA starter R.A. Dickey, who allowed four runs on six hits in four innings. “But if we take care of business the next two days, we should advance.”

That’s debatable. Considering Italy has a run differential of plus-11 going into Saturday and that Mexico is plenty capable of beating the Canadians, Team USA could need help to advance out of its pool, where the top two teams move on to the second round in Miami. If Mexico wins Saturday that gives the pool two teams with two wins before the United States even plays its second game.

Then Team USA has to beat Italy by at least three runs to make up for run differential, and baseball gods forbid, Mexico beats Canada in a blowout the way Italy did Friday.

Now the goal for Team USA is not only to win its two remaining games, but to do it in blowout fashion.

“(Italy) came out and got their two wins and got a lot of hits and a lot of runs,” USA shortstop Jimmy Rollins said. “So hopefully they are out of them.

“Hopefully they are happy with their two wins and I hope they are out drinking and partying it up, drinking that wine.”

When Rollins was asked if he realized his team could win its next two games and still not advance, he interrupted the question.

“That’s not happening,” Rollins said. “If we win the next two days, we’re advancing.”

Those two wins might not come if Team USA plays like they did Friday. Dickey, their best pitcher, couldn’t consistently find his killer knuckleball and was rocked. The big hit off him came in the third inning when Mexico and Los Angeles Dodgers first baseman Adrian Gonzalez launched a high knuckler over the wall in center field for a two-run homer and 4-0 lead.

The hitters weren’t any better. They couldn’t do much against Mexico and Milwaukee Brewer ace Yovani Gallardo, managing one run and two hits in his 3 1/3 innings. They stranded eight runners and were 2-for-13 with runners in scoring position.

Clearly, that all has to change Saturday against Italy, the hottest team in the tournament outside of the Dominican Republic. Ryan Vogelsong gets the ball for the States, but there is no question the lack of the best American-born players on the roster is at issue again.

There is no Justin Verlander, no Clayton Kershaw, no Stephen Strasburg and no secure feeling anymore that this team can do what needs to be done to advance beyond downtown Phoenix. Those names have valid reasons for not being here, and commissioner Bud Selig said during the game that he has no problems with some of the sports biggest stars opting out of the WBC.

Rollins also understands those reasons, and he believes there is only one thing that can bring the USA’s best aboard.

“The U.S. definitely has to win it,” he said as he looked and listened from the dugout to Mexican fans celebrating on the stadium’s main concourse. “This is America’s game, and we’re going to get everybody’s best.

“If you win, guys will be saying, ‘Hey, I want to be out there even if I’m only pitching one game.’ ”

But winning it all starts over Saturday night here at Chase Field. And it has to happen by more than a couple runs. If it doesn’t, count on plenty of columns and Tweets about how huge a failure this WBC has turned out to be for this country.